Air-jet spinning machines with suitably equipped spinning positions are known in the prior art (see, for example, EP 0 990 719 B1, DE 40 36 119 C2) and are used to produce yarn from an elongated fiber strand. The outer fibers of the fiber strand are wound around the inner core fibers with the help of a turbulent air stream created by the air jets within the turbulence chamber in the area of the aforementioned intake mouth of the yarn-forming element and they ultimately form the wrap fibers that are important for the desired strength of the yarn. This yields a yarn with a true twist, which is ultimately discharged from the turbulence chamber through the draw-off channel and can be wound onto a bobbin, for example.
In general, in the sense of the present invention, the term “yarn” is thus understood to be a fiber strand, in which at least some of the fibers are wound around an inner core. This therefore includes a yarn in the traditional sense, which can be processed to form a fabric with the help of a weaving machine. The invention also relates to air-jet spinning machines with the help of which so-called roving (another term: sliver or slubbing) can be produced. This type of yarn is characterized in that, despite a certain strength, which is sufficient to convey the yarn to a downstream textile machine, it is still capable of being drawn. The roving can thus be drawn with the help of a drafting device, e.g., a drawing stand, on a textile machine that processes the roving, for example, a ring spinning machine, before being finally spun.
However, regardless of the strength of the yarn, it is always desirable for the twist created in the area of the yarn-forming element not to extend over the inlet port opposite the conveyance direction of the yarn and/or the fiber strand. In other words, it should be ensured that the fibers of the fiber strand retain their original alignment before contact with the turbulent air stream and receive the corresponding twist only inside the turbulence chamber. In other words, if the twist were to propagate in a direction opposite the direction of conveyance, then the reverse twist of the fiber strand associated with this would necessarily lead to a reduction in the desired wrap fibers and/or to a reduced drawability of the fiber strand in the area of a drafting device upstream from the turbulence chamber.
The twist retaining elements, which act on the fiber strand from the outside and are already known in the prior art, restrict the corresponding propagation of twist, but on the other hand, a reduction in the wrap fibers must usually be accepted (see in particular the EP 0 990 719 B1 cited above).